Ca2+ entry through plasma membrane L-type (Cav1.2) Ca2+ channels regulates many essential biological functions including muscle contraction, hormone release, and gene expression. Dysregulation of L-type channel functional expression underlies a wide range of diseases including life-threatening atrial arrhythmias, autism, night blindness, and deafness. Moreover, L-type channels are important therapeutic targets for a number of diseases that constitute a significant detriment to the public health such as hypertension, angina, and arrhythmias. Nevertheless, there are significant gaps in knowledge regarding the precise role of L-type channels in the pathogenesis of various diseases, and their full therapeutic potential remains largely unrealized. A key contributor to the impasse is lack of fundamental mechanistic insights into processes underlying L-type channel sub-cellular targeting and gating behavior. Our long-term objective is two fold: first, to increase fundamental molecular understanding of structure-function mechanisms underlying L-type channel functional expression;second, to bridge these basic insights to a new realization of the (patho)physiological roles and therapeutic potential of L-type channels. We combine electrophysiological assays of recombinant and native L-type (Cav1.2) channels, FRET detection of protein interactions, and immounofluorescence detection of channel subunits in 4 Aims: 1. Clarify the role of auxiliary Cav[unreadable] structural determinants underlying trafficking and gating-modulation of recombinant L-type channel a1C subunits. 2. Clarify a1C structural determinants important for interacting with Cav[unreadable]s, and define their role in channel trafficking and gating-modulation. 3. Define the structural determinants underlying targeting of L-type Ca2+channels to dyadic junctions in heart. 4. Elucidate molecular determinants and mechanisms of protein kinase A modulation of cardiac L-type Ca2+channels.